The breathless pace that President Obama set after taking office last January jolted lawmakers from the soporific haze of the final George W. Bush years, revving up dormant committees and lighting up phone lines with a frenzy of dealmaking.

Wielding large Democratic majorities, House Speaker Nancy Pelosi (Calif.) and Senate Majority Leader Harry M. Reid (Nev.) relied on their expert vote-counting skills to send Obama 13 major bills and bring an overhaul of the nation's health-care system to the brink of final passage. By Christmas Eve, when the Senate finally adjourned, lawmakers were exuberant, if exhausted.

Then the bullet train screeched to a halt. Republican Scott Brown's victory in the Massachusetts special election on Tuesday cost the Democrats' their filibuster-proof Senate majority. Obama's biggest priorities -- overhauling health care, expanding college aid, reducing climate change -- are now in limbo, facing dim prospects as Republicans show little interest in cooperating, and Democrats brace for a 2010 midterm election year potentially as volatile as 1994, when the GOP captured the Senate and the House two years after Bill Clinton was elected president.

The agenda, Obama acknowledged Friday, had run into a "buzz saw" of opposition. "It's just an ugly process," he told an audience at an Ohio community college. "You're running headlong into special interests, and armies of lobbyists, and partisan politics that's aimed at exploiting fears instead of getting things done. And the longer it takes, the uglier it looks. . . . I can promise you there will be more fights ahead."

Obama asked Congress to take on so many issues in 2009, it was as if the entire Democratic Party platform was submitted for a vote. From closing Guantanamo Bay, to loosening Cuba policy, to transforming the way Wall Street is regulated and Pentagon weapons are acquired, Obama set a course that he described in his inaugural address as "the work of remaking America."

In his Election Night speech, Obama implored Democrats and Republicans alike, "Let us resist the temptation to fall back on the same partisanship and pettiness and immaturity that has poisoned our politics for so long."

And yet as the year unfolded, the divisions on Capitol Hill would only grow deeper, the rhetoric more hostile, the cooperation across the aisle less frequent and meaningful. The Senate, once a refuge of comity, is now as polarized as the House. And the president, rather than pushing back, relented.

Democratic leaders and White House officials insist they made the right decision to capitalize on the economic crisis and their outsize House and Senate majorities. Some of the bills that advanced in 2009 were perhaps too unwieldy for voters to digest and too easy for GOP opponents to demagogue. And six months of health-care talks may have suggested that Congress was ignoring more immediate problems, as Americans struggled to pay mortgages and tuition bills.

The challenge for Obama and his party now is to convince voters that it all adds up to progress.

"I viewed this year as the year we said we would do something, we did it, and now in this year of 2010, we'll talk about it," Pelosi said in an interview. "It's hard to talk about it when you're doing it."

Courting the GOP

The Obama legislative agenda was built around an "advancing tide" theory.

Democrats would start with bills that targeted relatively narrow problems, such as expanding health care for low-income children, reforming Pentagon contracting practices and curbing abuses by credit-card companies. Republicans would see the victories stack up and would want to take credit alongside a popular president. As momentum built, larger bipartisan coalitions would form to tackle more ambitious initiatives.

By the end of June, Congress had sent 10 major bills to Obama, including tougher tobacco regulations, a new public service initiative, and recession-related efforts to provide mortgage relief and curb predatory banking practices.

But Republican votes never materialized -- at least not in meaningful form that the White House had in mind. The first hint of GOP obstruction had emerged in January, when Obama made an early trip to Capitol Hill to urge support for his stimulus bill.

Standing at the microphones in the Ohio Clock corridor after the closed-door meeting with House Republicans, Obama expressed hope that his adversaries could "put politics aside" and support the bill.

But even as he spoke, House GOP leaders were urging their rank-and-file to vote against the rescue package. Obama had just departed when House Minority Leader John A. Boehner (Ohio) issued a statement calling the plan a "wasteful and unfocused package."

Democrats blamed the breakdown on Republican determination to undermine Obama. "If there's a political strategy not to cooperate, there's not a whole lot that you can do about it," said White House senior adviser David Axelrod.

The few GOP senators who sought consensus on health care concluded that Obama didn't have the patience to wait out protracted bipartisan negotiations in the Senate. Had those talks yielded a bill, it would likely have been smaller in scope than the White House had in mind, but Republicans would have shared its ownership.

Sen. Charles E. Grassley (R-Iowa), who worked for months on a bipartisan bill, said he decided Obama was not committed to meaningful compromise when he asked the president at an Aug. 6 White House meeting to take a stand against the government insurance option, a liberal favorite. Grassley said Obama did not answer him.

Democrats "know if they stick together, they'll get the job done," Grassley said before Brown's victory broke the filibuster-proof majority.

"They won the election. They're going to get it done even if the American people don't approve of it. And I think they're going to regret it."

Hands-off with Congress

In Reid and Pelosi, congressional Democrats were led by two battle-hardened politicians who had gained stature within their caucuses for their pragmatic determination.

Obama admires their no-nonsense approach, aides said. The trio talked frequently and met more than a half-dozen times in the Oval Office. In May, Obama headlined a fundraiser for Reid at Caesars Palace in Las Vegas. In October, the president's schedule showed a lunch with Pelosi in his private dining room.

Throughout, Obama ceded them ample authority. "The president set parameters or general principles of what he wants done," Axelrod said. "He's given them the latitude on how to achieve those ends."

But some Democrats would eventually complain that Obama was too hands-off, too absent, especially after tough votes.

When House Democrats passed energy legislation in June that included a controversial plan to curb carbon emissions, many returned home during a recess to angry constituents and found little support from the president.

House Democrats also complain about the missed political opportunity in the administration's muted response to what they consider one of their biggest 2009 victories -- a Dec. 11 vote to overhaul financial regulations. Republicans unanimously opposed the Wall Street crackdown.

"That bill got lost in the media focus on health-care reform," said Rep. Chris Van Hollen (Md.), chairman of the Democratic Congressional Campaign Committee. "But it exposes Republicans to the very fair charge that they have learned nothing. Of all the issues out there, that by far is the most potent."

White House advisers say Democrats need to understand that Obama is not all-powerful. "There is this sense on Capitol Hill that somehow the president can go out and make a speech and everything just magically becomes better," said a senior White House adviser who requested anonymity in order to speak frankly. "If there is a lesson out of the Massachusetts race, it is the people on Capitol Hill have to realize nobody can go win this for you. If you're going to cast the vote, then you have to be prepared to argue why it was the best vote."

For House Democrats, who enjoy a 256 to 178 majority, the main obstacle in 2009 was not Republicans, but the Senate. Even with 60 Democrats, Reid was unable to advance the climate-change and student loan bills that the House approved last summer. The Senate regulatory-reform bill is still in the banking committee.

Veteran House aides say Pelosi views her primary task as delivering Obama's agenda, but she also views herself as protector of her members and will push back if she thinks the White House is asking too much.

Late last year, Pelosi informed Obama that the 2010 House agenda would consist of job creation and deficit reduction. Her Democrats would take no more politically risky votes, she told him, until the Senate had cleared its backlog.

And that includes the health-care bill, Pelosi decided last week. As Brown delivered his victory speech in Boston on Tuesday, the speaker began canvassing House Democrats about prospects for approving the Senate version of the bill -- a vote that would send the legislation immediately to Obama. On Thursday morning, she announced she didn't have the votes.

"She's smart, she's articulate, she knows her issues," Obama told House Democrats of their speaker, during a retreat earlier this month. "But what people don't understand is, Nancy is tough. She is tough."

Neither Reid nor Pelosi has won over the general public, and one 2010 wild card is whether Reid's commitment to the Obama agenda will waver as he faces what could prove to be his toughest reelection campaign yet.

For dozens of hours over five days this month, Obama, Pelosi and Reid shuttered themselves inside White House with other top lawmakers and aides to try and reach a final deal on health care.

Brown's victory in Massachusetts crushed those hopes. The potential collapse of health care has exposed deep divisions among Democrats in recent days, as party leaders and the White House contemplate their next move. But when it became clear last week the House would not pass the Senate version, some Democrats began wondering if it was time to move on.

For months, lawmakers have quietly fumed that health care has eclipsed the economic concerns that remain foremost among their constituents. Their concerns were validated in Massachusetts, where polls showed Brown voters opposed the health-care bill and were alarmed about the economy.

House Democrats were the first to warn that the stimulus bill signed into law in February may not be enough to stem rising unemployment. On March 30, just before the House approved Obama's first budget on a party-line vote, the president made what would be his last appearance before either Democratic caucus until the health-care debate in the fall.

Rep. Peter A. DeFazio (D-Ore.), one of the few liberals to vote against the $787 billion stimulus plan because he wanted more infrastructure spending, reiterated his plea for additional funding. He was cut off.

"I know you think we need more for that, because you voted against it. Don't think we're not keeping score, brother," Obama replied, according to a person in the room. The lawmakers broke into laughter.

But the White House opposed House efforts to advance a new, massive job-creating transportation bill in the summer. By September, fearing the economy was not turning around fast enough, Pelosi began expressing concerns to Obama in their private discussions. She convened a panel of economists and ordered her committee chairmen to begin compiling what would become a $154 billion stimulus proposal approved by the House before Christmas.

Before the Massachusetts loss, the White House officials touted 2009 as the most productive legislative year in decades. Prodded before Tuesday's election whether Obama and his team would change anything about its Hill strategy, Axelrod replied, "I've thought about that and I don't see how."

Lawmakers expect Obama to set a course for 2010 on Wednesday, in his State of the Union speech. Democrats want the focus on one issue: jobs. But on Friday in Ohio, given a few days to digest Brown's upset, Obama defended and promoted the same long to-do list he brought with him to office.

"I didn't run for president to turn away from these challenges," he said. "I didn't run for president to kick them down the road. I ran for president to confront them -- once and for all."